We plan to continue investigations of the subunit structure and oxygen binding properties of Callianassa hemocyanin. Having found conditions under which the association reaction can be limited to monomer-dimer or dimer-tetramer equilibria, we can now examine the allosteric behavior of the O2 binding when specific aggregation states are present. Another line of research will center on the discovery that the protein is microheterogeneous in its polypeptide chains. We intend to separate chains, and then reconstitute active hemocyanin molecules from various combinations. The oxygen binding of such molecules will be studied.